[go] internal/bytealg: unexport {Last,}IndexRabinKarp helpers

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Tobias Klauser (Gerrit)

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Feb 4, 2026, 10:30:22 AM (3 days ago) Feb 4
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internal/bytealg: unexport {Last,}IndexRabinKarp helpers

After CL 538737 these no longer need to be exported. They are only
used in internal/bytealg and can be unexported.
Change-Id: Idd405f397c7ec9f96425d2b7e0e74de61daa7a6e

Change diff

diff --git a/src/internal/bytealg/bytealg.go b/src/internal/bytealg/bytealg.go
index 319ea54..57a1e4d 100644
--- a/src/internal/bytealg/bytealg.go
+++ b/src/internal/bytealg/bytealg.go
@@ -29,17 +29,17 @@
 // If MaxLen is not 0, make sure MaxLen >= 4.
 var MaxLen int
 
-// PrimeRK is the prime base used in Rabin-Karp algorithm.
-const PrimeRK = 16777619
+// primeRK is the prime base used in Rabin-Karp algorithm.
+const primeRK = 16777619
 
-// HashStr returns the hash and the appropriate multiplicative
+// hashStr returns the hash and the appropriate multiplicative
 // factor for use in Rabin-Karp algorithm.
-func HashStr[T string | []byte](sep T) (uint32, uint32) {
+func hashStr[T string | []byte](sep T) (uint32, uint32) {
 	hash := uint32(0)
 	for i := 0; i < len(sep); i++ {
-		hash = hash*PrimeRK + uint32(sep[i])
+		hash = hash*primeRK + uint32(sep[i])
 	}
-	var pow, sq uint32 = 1, PrimeRK
+	var pow, sq uint32 = 1, primeRK
 	for i := len(sep); i > 0; i >>= 1 {
 		if i&1 != 0 {
 			pow *= sq
@@ -49,14 +49,14 @@
 	return hash, pow
 }
 
-// HashStrRev returns the hash of the reverse of sep and the
+// hashStrRev returns the hash of the reverse of sep and the
 // appropriate multiplicative factor for use in Rabin-Karp algorithm.
-func HashStrRev[T string | []byte](sep T) (uint32, uint32) {
+func hashStrRev[T string | []byte](sep T) (uint32, uint32) {
 	hash := uint32(0)
 	for i := len(sep) - 1; i >= 0; i-- {
-		hash = hash*PrimeRK + uint32(sep[i])
+		hash = hash*primeRK + uint32(sep[i])
 	}
-	var pow, sq uint32 = 1, PrimeRK
+	var pow, sq uint32 = 1, primeRK
 	for i := len(sep); i > 0; i >>= 1 {
 		if i&1 != 0 {
 			pow *= sq
@@ -70,17 +70,17 @@
 // first occurrence of sep in s, or -1 if not present.
 func IndexRabinKarp[T string | []byte](s, sep T) int {
 	// Rabin-Karp search
-	hashss, pow := HashStr(sep)
+	hashss, pow := hashStr(sep)
 	n := len(sep)
 	var h uint32
 	for i := 0; i < n; i++ {
-		h = h*PrimeRK + uint32(s[i])
+		h = h*primeRK + uint32(s[i])
 	}
 	if h == hashss && string(s[:n]) == string(sep) {
 		return 0
 	}
 	for i := n; i < len(s); {
-		h *= PrimeRK
+		h *= primeRK
 		h += uint32(s[i])
 		h -= pow * uint32(s[i-n])
 		i++
@@ -95,18 +95,18 @@
 // occurrence of sep in s, or -1 if not present.
 func LastIndexRabinKarp[T string | []byte](s, sep T) int {
 	// Rabin-Karp search from the end of the string
-	hashss, pow := HashStrRev(sep)
+	hashss, pow := hashStrRev(sep)
 	n := len(sep)
 	last := len(s) - n
 	var h uint32
 	for i := len(s) - 1; i >= last; i-- {
-		h = h*PrimeRK + uint32(s[i])
+		h = h*primeRK + uint32(s[i])
 	}
 	if h == hashss && string(s[last:]) == string(sep) {
 		return last
 	}
 	for i := last - 1; i >= 0; i-- {
-		h *= PrimeRK
+		h *= primeRK
 		h += uint32(s[i])
 		h -= pow * uint32(s[i+n])
 		if h == hashss && string(s[i:i+n]) == string(sep) {

Change information

Files:
  • M src/internal/bytealg/bytealg.go
Change size: S
Delta: 1 file changed, 16 insertions(+), 16 deletions(-)
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Keith Randall (Gerrit)

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    Gopher Robot (Gerrit)

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    Change information

    Commit message:
    internal/bytealg: unexport {Last,}IndexRabinKarp helpers

    After CL 538737 these no longer need to be exported. They are only
    used in internal/bytealg and can be unexported.
    Change-Id: Idd405f397c7ec9f96425d2b7e0e74de61daa7a6e
    Reviewed-by: Keith Randall <k...@golang.org>
    Reviewed-by: Michael Pratt <mpr...@google.com>
    Auto-Submit: Tobias Klauser <tobias....@gmail.com>
    Reviewed-by: Keith Randall <k...@google.com>
    Files:
    • M src/internal/bytealg/bytealg.go
    Change size: S
    Delta: 1 file changed, 16 insertions(+), 16 deletions(-)
    Branch: refs/heads/master
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    Gerrit-Change-Number: 741920
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